Section A — 1 Mark Questions
1. What are the five basic components of a data communication system? [1 Mark]
Answer: The five components are the message, sender, receiver, transmission medium, and protocol.
2. Define data communication. [1 Mark]
Answer: Data communication is the exchange of data between two devices via some form of transmission medium.
3. Name the three fundamental characteristics of an effective data communication system. [1 Mark]
Answer: Delivery, accuracy, and timeliness.
4. What is the main cause of jitter in data communication? [1 Mark]
Answer: Jitter is caused by variations in the packet arrival time at the receiver.
5. Which transmission mode allows data to flow in both directions, but not simultaneously? [1 Mark]
Answer: Half-duplex mode.
6. Define simplex transmission. [1 Mark]
Answer: Simplex transmission is a unidirectional communication mode where only one device can send data.
7. What is the primary function of a protocol in data communication? [1 Mark]
Answer: A protocol defines the rules that govern data communication, including syntax, semantics, and timing.
8. List the three major transmission impairments. [1 Mark]
Answer: Attenuation, distortion, and noise.
9. What does the 'semantics' element of a protocol refer to? [1 Mark]
Answer: It refers to the meaning of each section of bits and how they should be interpreted.
10. Define attenuation. [1 Mark]
Answer: Attenuation is the loss of signal strength as it travels through a medium.
11. Which mode of transmission allows simultaneous bi-directional data flow? [1 Mark]
Answer: Full-duplex mode.
12. What is the role of the 'sender' in a communication system? [1 Mark]
Answer: The sender is the device that originates the data message.
13. What is 'noise' in the context of signal impairment? [1 Mark]
Answer: Noise refers to unwanted electrical or electromagnetic energy that corrupts the signal.
14. What does 'timing' signify in a protocol? [1 Mark]
Answer: Timing refers to when data should be sent and how fast it should be transmitted.
15. Define a transmission medium. [1 Mark]
Answer: It is the physical path by which a message travels from sender to receiver.
16. What is meant by 'data delivery' as a characteristic? [1 Mark]
Answer: Data delivery means the system must transmit data to the correct destination.
17. How is 'distortion' different from 'attenuation'? [1 Mark]
Answer: Attenuation is loss of strength, whereas distortion is a change in the form or shape of the signal.
18. What is the purpose of the 'message' component? [1 Mark]
Answer: The message is the information (data) to be communicated.
19. Can a half-duplex system act as a simplex system? [1 Mark]
Answer: No, because they are distinct modes based on directional capacity and timing.
20. What is the role of the receiver? [1 Mark]
Answer: The receiver is the device that accepts the message sent by the sender.
Section B — 2/3 Mark Questions
1. Briefly explain the concept of 'delivery' and 'accuracy' in data communication. [2 Marks]
Answer: Delivery ensures that the data is delivered to the intended destination device. Accuracy ensures that the system delivers data without errors and that the data received is identical to the data sent.
2. Distinguish between full-duplex and half-duplex transmission modes. [2 Marks]
Answer: In half-duplex, both stations can transmit, but not simultaneously. In full-duplex, both stations can transmit and receive data at the same time.
3. What are the three key elements of a protocol? [3 Marks]
Answer: 1. Syntax: The structure or format of the data. 2. Semantics: The meaning of each section of bits. 3. Timing: When data should be sent and how fast it should be transmitted.
4. Why is 'timeliness' a critical characteristic of data communication? [2 Marks]
Answer: Timeliness ensures that data is delivered in a timely manner. Late delivery of data is useless, especially in real-time applications like audio or video streaming.
5. Explain how attenuation affects a signal. [2 Marks]
Answer: Attenuation refers to the loss of energy as a signal propagates. It means the signal's strength decreases, often requiring amplifiers or repeaters to restore the signal level.
6. Describe the simplex mode of transmission with an example. [3 Marks]
Answer: In simplex mode, communication is unidirectional. Only one device can transmit; the other can only receive. An example is a television broadcast, where the station sends signals to the television.
7. Briefly discuss how noise impacts data communication. [3 Marks]
Answer: Noise includes thermal, induced, crosstalk, or impulse noise. It adds unwanted energy to the signal, which can interfere with the original data and lead to errors in the interpretation of bits by the receiver.
8. What is the difference between a sender and a receiver? [2 Marks]
Answer: The sender is the device that creates and transmits the data. The receiver is the device that accepts the data. In bi-directional communication, roles can switch.
9. How does distortion occur during transmission? [3 Marks]
Answer: Distortion occurs when the signal changes its form or shape. This typically happens in composite signals made of different frequencies, where each frequency component travels at a different speed, causing the signal to arrive out of phase or changed at the destination.
10. Explain the role of a transmission medium. [2 Marks]
Answer: The medium provides the physical path (wired or wireless) through which electromagnetic signals travel to carry data from the source to the destination.
Section C — 5 Mark Questions
1. Explain the five fundamental components of a data communication system in detail. [5 Marks]
Answer:
Components
- Message: The actual information, such as text, numbers, images, or video, that is being communicated.
- Sender: The hardware device that generates the message to be transmitted.
- Receiver: The hardware device that accepts the message from the network.
- Transmission Medium: The physical path, such as twisted-pair cable, fiber optics, or radio waves, that connects the sender and receiver.
- Protocol: A set of governing rules that enable devices to communicate successfully, ensuring synchronization and data integrity.
2. Discuss the three transmission modes used in data communication. [5 Marks]
Answer:
Simplex
In this mode, communication is unidirectional. Only one device can send data, while the other can only receive it. Examples include keyboards and traditional radio broadcasting.
Half-Duplex
In this mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other must wait. A walkie-talkie is a classic example.
Full-Duplex
In this mode, both stations can transmit and receive simultaneously. Signals go in both directions at the same time. The telephone network is a primary example of full-duplex communication.
3. Elaborate on the three main types of transmission impairments in data communication. [5 Marks]
Answer:
Attenuation
Attenuation is the loss of signal strength. As a signal travels through a medium, it loses energy due to the resistance of the medium. Engineers use amplifiers to boost the signal strength to compensate for this loss.
Distortion
Distortion occurs when a signal changes its shape or form. This is common in signals composed of multiple frequencies where each frequency travels at a different velocity, leading to signal delay or phase shift.
Noise
Noise refers to external signals that interfere with the original signal. Common types include thermal noise (electron agitation), induced noise (motors/appliances), and crosstalk (interference between wires). Noise can cause bits to be incorrectly interpreted at the receiving end.
4. Describe the importance of the three key characteristics of an effective data communication system. [5 Marks]
Answer:
Delivery
The system must deliver data to the correct destination. Data must be received by the device for which it is intended, not any other node on the network.
Accuracy
The system must deliver data accurately. If bits are altered during transmission, the resulting data is corrupted and useless. Error detection and correction mechanisms are essential to maintain accuracy.
Timeliness
Data must be delivered in a timely manner. Data delivered late is ineffective, particularly in time-sensitive communications such as video conferencing, financial trading, or remote surgical procedures, where delays (jitter) can lead to service failure.
5. Explain the composition and functions of a communication protocol. [5 Marks]
Answer:
Composition
A protocol is essentially a language used by network components. It consists of three key elements: Syntax, Semantics, and Timing.
Functions
- Syntax: Defines the structure or format of the data. It dictates how the data is organized, including the ordering and framing of bits.
- Semantics: Defines the meaning of each section of bits. It specifies the action or interpretation required by the receiver for specific bit patterns.
- Timing: Defines two characteristics: when data should be sent and how fast it should be sent. This prevents buffer overflows and ensures that the sender and receiver are synchronized.
Without protocols, devices would be unable to understand the incoming signals, making network communication impossible.